Thanks, Chris. I'm going to give it a couple more days to see if the missing file situation resolves itself. I removed the smb version of the NAS and and added a share for the afs version.
This has resulted in a couple of the missing files now appearing but there is still one not showing. It is a big one with several sub-folders. Maybe it will appear eventually. Messages in MDP keep telling me some folder or other is still being built so let's wait and see. If still not resolved in a day or two I will switch to service mode and let you know.